stellar-core will automatic maintenance.Maintenance code:main/Maintainer.cpp. it will delete old data in maintenance process,how to view the deleted data?
Stellar core can save old history in xdr files https://github.com/stellar/stellar-core/blob/master/docs/history.md
Stellar's blockchain history isnt preserved inside the core's database (or at least, it isnt necessarily saved there). Rather, the core uploads the history to some pre-set location, like an S3 bucket or wherever. The idea is that this place needs to be public, so other cores can read it if/when they start up.